In cancer patients, determination of whether a malignancy has spread is the single most important factor used to develop a therapeutic plan and to predict prognosis. In most cases, cancer cells initially spread through regional lymph nodes. Therefore, clinical evaluation for the presence of regional lymph node metastases is of paramount importance. Unfortunately, there are no real-time, non-invasive clinical methods that can reliably detect and diagnose micrometastases in lymph nodes. Therefore, there is an urgent clinical need for an imaging technique that is widely available, is non-invasive and simple to perform, is safe, and can reliably detect and adequately diagnose lymph node micrometastases in real time. The overall goal of our research program is to develop an advanced, in-vivo, noninvasive, molecular specific imaging technology, i.e., integrated ultrasound and photoacoustic imaging combined with targeted plasmonic nanosensors, capable of immediate and accurate assessment of sentinel lymph node micrometastases in real time. The underlying hypothesis of this project is that photoacoustic imaging integrated with widely used clinical ultrasound imaging is possible and both ultrasound and photoacoustic imaging can be performed in real time, yielding an immediate diagnosis and allowing early implementation of treatment. A wide range of scientific and engineering, biomedical and clinical problems must be addressed to fully explore the capabilities of molecular specific ultrasound and photoacoustic lymphatic (MS-USPAL) imaging in detection and characterization of sentinel lymph node micrometastases. The current application is focused on important aspects of clinical translation of MS-USPAL imaging. We will develop and validate clinically translatable plasmonic nanosensors for MS-USPAL. We will use ultra-small gold nanoparticles to target epidermal growth factor receptor (EGFR), which is overexpressed in squamous carcinoma and in many other epithelial neoplasms. For highly sensitive detection of cancer cells, we will explore EGF receptor mediated endocytosis and the effect of plasmon resonance coupling between closely spaced molecular specific nanoparticles. The ultra-small size of nanoparticles will be highly favorable for rapid clearance from the body which will allow safe transition into clinical practice Additionally, 5 nm ligand capped gold nanoparticles will greatly reduce nonspecific interactions and reduce the uptake of nanoparticles by immune cells such as macrophages present due to lymph node inflammation, thus diminishing false positive results. Furthermore, we will design and construct a prototype of the clinical MS-USPAL imaging system capable of imaging 5 nm nanoparticles in-vivo.